1. Field of the Invention
This invention relates generally to a magnetic sensor, and more particularly to a magnetic head and a magnetic memory used for computers and information processing units.
2. Description of the Related Art
Magnetic recording media have been predominantly magnetic disks and magnetic tapes. They are manufactured by forming a thin magnetic film on an Al substrate or a resin tape. A magnetic head utilizing an electromagnetic conversion operation is used in order to write and read magnetic information to and from these magnetic media. This magnetic head comprises a write portion for writing the magnetic information to the recording medium and a read portion for reading out the magnetic information from the recording medium. A so-called xe2x80x9cinduction type headxe2x80x9d, which comprises a coil and magnetic poles that wrap the coil from above and below and are electrically connected to the coil, is generally used for the write portion. Magneto-resistance effect (MR) heads have been proposed recently for the read portion so as to cope with the magnetic information having a high recording density. Among the MR heads, those heads which utilize the gigantic magneto-resistance effect (GMR) are well known nowadays.
Recently, a magnetic sensor using a ferromagnetic tunnel magneto-resistance effect (spin tunnel magneto-resistance effect: TMR) has been proposed for a magnetic memory as described in JP-A-10-4227. This TMR can obtain a greater resistance change ratio by causing a current to flow in a direction of film thickness of the magneto-resistance effect film than the conventional magneto-resistance effect devices such as the GMRs which cause a current to flow in a direction of the main plane of the magneto-resistance effect film.
According to the construction described in JP-A-10-4227, however, an upper electrode stack 30 comprising at least a free ferromagnetic layer 32 and a protective layer 34 must be formed inside a contact hole defined in an insulating layer 40. Therefore, production is difficult, and film quality and film thickness of each layer inside the contact hole are likely to fluctuate from a desired level.
In view of the problems described above, the present invention aims at providing a construction of a magnetic sensor using a spin tunnel magneto-resistance effect (TMR) which construction can be manufactured more easily than the prior art devices and can stably keep film quality and thickness at a desired level, and a method of producing the magnetic sensor.
To accomplish the object, a spin tunnel magneto-resistance effect magnetic sensor according to the present invention comprises a first insulating film which allows a current to tunnel and flow therethrough, a first magnetic layer formed on a first surface of the first insulating film and containing a ferromagnetic substance, a second magnetic layer formed on a second surface of the first insulating film and containing a ferromagnetic substance, a third magnetic layer formed on the second magnetic layer and containing an anti-ferromagnetic substance for fixing magnetization of the second magnetic layer, a second insulating film formed on at least one of the first and third magnetic layers and having an opening in a predetermined region, a first electrode electrically connected to one of the first and third magnetic layers only inside the opening of the second insulating film, and a second electrode for causing a current to flow between at least one of the first and second magnetic layer and the first electrode through the first insulating film.
A method of producing a spin tunnel magneto-resistance effect type magnetic sensor having a first magnetic layer containing a ferromagnetic substance, a second magnetic layer containing a ferromagnetic substance and a third magnetic layer containing an anti-ferromagnetic substance for fixing magnetization of the second magnetic layer according to the present invention comprises the steps of (a) forming the third magnetic layer over a substrate by sputtering, (b) forming the second magnetic layer on the third magnetic layer by sputtering, (c) processing at least the second and third magnetic layers into a first pattern, (d) forming a first insulating film, which allows an electric current to tunnel and flow there-through, on at least the first pattern, by sputtering, (e) forming a first magnetic layer on the first insulating film by sputtering, (f) processing at least the first magnetic layer and the first insulating film into a second pattern, (g) forming a second insulating film in at least a predetermined region of the second pattern, (h) forming an opening in a predetermined region of the second insulating film and (i) forming a first electrode, which is electrically connected to the first magnetic layer only inside the opening of the second insulating film, and forming a second electrode electrically connected to the second magnetic layer.